Seventy-two (54.5%) out of 132 fecal samples from a group of yellowlegged gulls in Barcelona, Spain, were positive for Escherichia coli producing either extended-spectrum -lactamases (ESBL) (51.5%), carbapenemase (1.5%), or cephamycinase (1.5%). The isolation of two carbapenemase-producing E. coli strains is a matter of concern.KEYWORDS carbapenemases, E. coli, ESBL I n the last decade, the number of bacterial pathogens presenting multidrug resistance to antibacterial agents has increased dramatically, becoming an emergent global concern and a major public health problem (1). The main cause behind the increasing rates of resistance can ultimately be found in the abuse and misuse of antibacterial agents, whether used in patients and livestock or released into the environment. Once antimicrobial-resistant bacteria emerge, they can spread locally or globally. The main factors contributing to their spread at a global level comprise migrant birds, globalization of commercial food, and international travel.There have been several studies about the presence of resistant bacteria in gulls (2, 3), to the extent of being considered an indicator of environmental antibiotic resistance occurrence, as they are distributed almost all around the world (4). Meerburg et al. (5) showed that gull feces contain a greater average concentration of E. coli than other wild animals, and according to Stedt et al. (4), Spain is the country in Europe with the highest levels of gull E. coli isolates resistant to Ն1 antibiotic.The objective of this study was to investigate the prevalence of extended-spectrum -lactamase (ESBL)-and/or carbapenemase-producing Enterobacteriaceae from fecal swabs obtained from a group of yellow-legged gulls (Larus michahellis) in Barcelona, Spain.The study was conducted from the beginning of May to late July 2014 in the city of Barcelona, including the breeding period of the yellow-legged gull in the city. The sampling program was part of the sanitary and epidemiological surveillance that is carried out by the Public Health Agency, Barcelona, the institution responsible for the supervision and surveillance of the species. The sampling sites were chosen according to citizens' reports regarding the species nesting on their terraces or high roofs of the city. Every gull chick from each nest found (Fig. 1) was sampled, which amounts to 132 samples in total. All samples were obtained from young specimens born in that same year, and all nests were independent from each other, since the urban structure of cities The samples were plated on ESBL chromogenic agar (bioMérieux, France), and burgundy red colonies were selected, according to the manufacturer's instructions. Colonies were further identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) (Bruker Daltonics, Inc., Bremen, Germany). Susceptibility to ampicillin, amoxicillin-clavulanic acid, cefuroxime, ceftriaxone, cefotaxime, meropenem, gentamicin, amikacin, nalidixic acid, and ciprofloxacin was determined ...